Typically, these frequent fliers are automatically checked in for their flight 36 hours in advance, giving them a leg-up in Southwest’s group boarding process compared to other fliers who have to manually check in up to 24 hours in advance.

But travelers started reporting over the weekend that they weren’t being automatically checked in as expected, causing their boarding position to fall, in some cases dropping them out of the coveted A boarding group.

The problems prompted expressions of frustration and unhappiness on social media from affected travelers.

We're so sorry for the frustration, and our Technology folks are aware of the error. We hope to have a fix soon. Hang in there with us. ^SO

Southwest described the problem as an “ongoing issue” and said its technology team is “working feverishly” to resolve it. There is currently no estimated timeline for when a fix will be in place, a company spokeswoman said.

“This has resulted in boarding positions that are less typical than what our A-List and A-List Preferred Rapid Rewards Customers have come to expect,” Southwest said in a statement. “We apologize for any inconvenience to our customers.”

In a message sent to affected customers Monday, Southwest recommended they check in manually for their flights 24 hours in advance if they’re traveling in the “next several days.”

The company also reminded those frequent fliers with A-List or A-List Preferred status that they’re always able to board the plane between the A and B groups, regardless of the boarding position printed on their ticket.

The issues come several months after Southwest completed a major technology transition to a new reservations system. While the company avoided major operational problems when the system went live in May, CEO Gary Kelly acknowledged last month that there were a few technical issues that were preventing it from reaching its full potential.

One of the issues Kelly detailed dealt with a process for selling upgraded boarding to customers at the gate that was not working as intended.

“These are just a couple of one-off items that we found, that we'll fix and we'll get behind us,” Kelly told analysts in July.